1. Field of the Invention
The present invention relates to a method and apparatus for improving a reconfiguration procedure for Scheduling Request, and more particularly, to a method and apparatus for improving a reconfiguration procedure for Scheduling Request in a user equipment (UE) of a wireless communication system, so as to appropriately reconfigure parameters corresponding to a Scheduling Request procedure.
2. Description of the Prior Art
Long Term Evolution wireless communication system (LTE system), an advanced high-speed wireless communication system established upon the 3G mobile telecommunication system, supports only packet-switched transmission, and tends to implement both Medium Access Control (MAC) layer and Radio Link Control (RLC) layer in one single communication site, such as in Node B (NB) alone rather than in NB and RNC (Radio Network Controller) respectively, so that the system structure becomes simple.
In LTE system, based on 3GPP technical specification TS 36.321 V8.4.0, when the UE has new uplink data to transmit such as a Regular Buffer Status Report (BSR) and there is no Uplink Shared Channel (UL-SCH) resource for new transmission available, the UE shall trigger a Scheduling Request (SR) to request the network to allocate uplink resources . In such a situation, if the UE has configured valid Physical Uplink Control Channel (PUCCH) resources for SR, the SR is transmitted on PUCCH. Otherwise, such as the UE has no configured PUCCH resources for SR or the configured PUCCH resources for SR are invalid, for example, the UE shall initiate a Random Access Procedure to request the network to allocate uplink resources.
When an SR is triggered, it shall be considered as pending until it is cancelled. Besides, if an SR is triggered and there is no other SR pending, the UE shall set a counter SR_COUNTER, which is utilized for counting the number of SR transmission times in the SR procedure, to 0. That is to initialize the counter SR_COUNTER.
As long as one SR is pending, if the UE has a valid PUCCH resource for SR transmission, the UE shall periodically transmit the SR on PUCCH until an UL-SCH resource for a new transmission is received or the number of SR transmissions reaches to a pre-defined parameter dsr-TransMax. Whenever the SR is transmitted, the counter SR_COUNTER is incremented by 1. If the number of SR transmissions reaches to the pre-defined parameter dsr-TransMax, it indicates uplink transmission of the UE may have some problem, such as the PUCCH resources for SR become invalid (probably due to poor signal quality or improper power settings) or the UE loses synchronization on uplink timing, and thus the SR sent on PUCCH cannot be successfully received by the network. In this case, the UE shall cancel all pending SR(s) i.e. stop the SR transmission, release uplink resources such as all configured PUCCH resources and SRS resources for transmitting uplink Sounding Reference Signals, and initiate a Random Access procedure. Besides, when the UE receives an UL-SCH resource for a new transmission, all pending SR(s) shall be cancelled.
On the other hand, upper layers such as Radio Resource Control (RRC) layer would request the UE to perform a reconfiguration procedure to reconfigure parameters corresponding to the SR procedure, such as dsr-TransMax, sr-PUCCH-ResourceIndex and sr-ConfigurationIndex, for example. According to current specifications, if reconfiguration is requested by upper layers, the UE shall immediately apply new configurations received from the upper layers.
However, for some parameters such as SR parameters, immediately applying the new configurations received from the upper layers may cause UE errors. For example, when the UE has pending SR (s) and reconfiguration is requested by the upper layers, if the UE immediately applies the new configurations to the SR parameter dsr-TransMax, the counter SR_COUNTER may thus exceed the parameter dsr-TransMax, resulting in that the UE unnecessarily releases uplink resources and initiates a Random Access procedure. Therefore, there is a need to improve the reconfiguration procedure for SR.